Method and apparatus for initial access in wireless communication system

1. A method performed by a wireless device in a wireless communication system, the method comprising:

camping on a first cell;

receiving, from the first cell the wireless device camps on, system information, wherein the system information comprises information informing one or more candidate cells for a duplicated access including a second cell;

measuring a signal quality of the first cell and a signal quality of the second cell; and

based on a determination that the signal quality of the first cell and the signal quality of the second cell are within an offset, performing an initial access to both of the first cell and the second cell, wherein the performing of the initial access to both of the first cell and the second cell comprises:

transmitting a first random access preamble to the first cell and a second random access preamble to the second cell;

receiving a first random access response comprising a first uplink grant from the first cell, and a second random access response comprising a second uplink grant from the second cell, after transmitting the first random access preamble, and the second random access preamble;

transmitting a first connection request message based on the first uplink grant via a physical uplink shared channel (PUSCH) to the first cell, and a second connection request message based on the second uplink grant via a PUSCH to the second cell, wherein the second connection request message is a duplicate connection request message of the first connection request message; and

after transmitting the first connection request message and the second connection request message, receiving, at least one of a first connection response message via a physical downlink shared channel (PDSCH) from the first cell, or a second connection response message via a PDSCH from the second cell.

2. The method of claim 1 , wherein the signal quality of the first cell and the signal quality of the second cell are above a threshold that is configured by a network or is a predetermined value.

3. The method of claim 1 , wherein the wireless device is in an idle mode or an inactive mode.

4. The method of claim 1 , wherein the offset is configured by a network, or is a predetermined value.

5. The method of claim 1 , wherein the signal quality of the second cell is within the offset below the signal quality of the camped cell.

6. The method of claim 1 , wherein the performing of the initial access to both of the first cell and the second cell comprises:

receiving, from the first cell, a connection reject message for the first connection request message transmitted to the first cell; and

stopping a random access for the first cell based on the connection reject message, wherein a random access for the second cell continues being performed while the random access for the first cell is stopped.

7. The method of claim 1 , wherein the performing of the initial access to both of the first cell and the second cell comprises:

receiving, from the first cell, a connection reject message for the first connection request message transmitted to the first cell; and

stopping both of a random access for the first cell and a random access for the second cell based on the connection reject message received from the first cell.

8. The method of claim 1 , wherein the wireless device is in communication with at least one of a user equipment, a network, or autonomous vehicles other than the wireless device.

9. A wireless device in a wireless communication system comprising:

a transceiver;

a memory; and

at least one processor operatively coupled to the transceiver and the memory, and configured to:

camp on a first cell,

control the transceiver to receive, from the first cell the wireless device camps on, system information, wherein the system information comprises information informing one or more candidate cells for a duplicated access including a second cell,

measure a signal quality of the first cell and a signal quality of the second cell, and

based on a determination that the signal quality of the first cell and the signal quality of the second cell are within an offset, perform an initial access to both of the first cell and the second cell, wherein the performing of the initial access to both of the first cell and the second cell comprises:

transmitting a first random access preamble to the first cell and a second random access preamble to the second cell;

receiving a first random access response comprising a first uplink grant from the first cell, and a second random access response comprising a second uplink grant from the second cell, after transmitting the first random access preamble, and the second random access preamble;

transmitting a first connection request message based on the first uplink grant via a physical uplink shared channel (PUSCH) to the first cell, and a second connection request message based on the second uplink grant via a PUSCH to the second cell, wherein the second connection request message is a duplicate connection request message of the first connection request message; and

after transmitting the first connection request message and the second connection request message, receiving, at least one of a first connection response message via a physical downlink shared channel (PDSCH) from the first cell, or a second connection response message via a PDSCH from the second cell.

10. A processor for a wireless device in a wireless communication system, wherein the processor is configured to control the wireless device to perform operations comprising:

camping on a first cell;

receiving, from the first cell the wireless device camps on, system information wherein the system information comprises information informing one or more candidate cells for a duplicated access including a second cell;

measuring a signal quality of the first cell and a signal quality of the second cell; and

based on a determination that the signal quality of the first cell and the signal quality of the second cell are within an offset, performing an initial access to both of the first cell and the second cell, wherein the performing of the initial access to both of the first cell and the second cell comprises:

transmitting a first random access preamble to the first cell and a second random access preamble to the second cell;

receiving a first random access response comprising a first uplink grant from the first cell, and a second random access response comprising a second uplink grant from the second cell, after transmitting the first random access preamble and the second random access preamble;

transmitting a first connection request message based on the first uplink grant via a physical uplink shared channel (PUSCH) to the first cell, and a second connection request message based on the second uplink grant via a PUSCH to the second cell, wherein the second connection request message is a duplicate connection request message the first connection request message; and

after transmitting the first connection request message and the second connection request message, receiving at least one of a first connection response message via a physical downlink shared channel (PDSCH) from the first cell, or a second connection response message via a PDSCH from the second cell.